Currently the usage of CancelableOperationContexts lead to unspecific errors being thrown when these opCtxes are interrupted. There is a narrow window in setFCV we use a CancelableOperationContext to do internal session cleanup where interruptions would result in a nonretryable error being thrown. This causes internal_sessions_setfcv_wait_for_transaction_coordinator_cleanup.js to be a bit flaky since it relies on the retryablility of the setFCV on stepdown.